
Aadhaar card number or Unique Identity Number is to be linked with mobile SIMs by March 31, 2018
Bharti Airtel and Vodafone India, among others, have activated this service 14546 facility for linking of mobile number with Aadhaar.
Bharti Airtel has, for example, set up the toll-free, IVRS-based facility 14546 to assist their customers in the Aadhaar verification process. According to Bharti Airtel's website, the telecom company's customers can verify their mobile number with Aadhaar "sitting at home" through the toll-free helpline 14546. "...Call 14546 (toll-free). OTP (One-Time Pin) will be sent to your number registered in Aadhaar database," Bharti Airtel mentions on its website."You can easily verify your mobile connections from anywhere by simply dialing 14546.
— Aadhaar (@UIDAI) February 12, 2018
Aadhaar registered mobile number mandatory to get OTP to complete the verification process.#VerifyWithAadhaar" pic.twitter.com/mCVMdfOUa3

Vodafone India has on its website listed eight steps for its customers to re-verify their mobile number with Aadhaar via IVR. Mobile phone subscribers of other telecom companies may check with their telecom operator for such a facility.
How to link Vodafone India mobile number with Aadhaar via IVRS by dialing 14546, according to the telecom company's website - vodafone.in:
1. Call 14546
2. Provide consent
3. Enter Aadhaar number
4. Give approval
5. Key in OTP to validate
6. Total number of mobile connections
7. Enter each such mobile number
8. Wait for confirmation SMS

This method, explains Vodafone India, requires the mobile number the customer wants to re-verify, the Aadhaar number of the customer, the mobile number registered with Aadhaar (for receiving OTP or One-Time PIN) and any other mobile number on the customer's name (provided by Vodafone or any other company).